Bacterial ID Lab at Howard Hughes Medical Institute

google doc


The procedures necessary for extracting and isolating DNA of an unknown bacteria are costly, time consuming, and can even be dangerous in that it can expose a lab technician to pathogens. Fortunately, technology has given us virtual labs that will show how these procedures are done without the mess and the fuss. In this internet activity, you will use a virtual lab to perform the following procedures:

Instructions: The virtual lab is divided into six sections that walk you through the procedures involved. Don't forget to read the notebook section as well, which has further explanation about what you are doing and why. As you complete each section, answer the corresponding questions.

Sample Prep

1. The first step in the extraction process uses a wire loop to do what?

2. Why are the digestive enzymes necessary for DNA extraction?

3. The centrifuge separates the cellular content into two distinct layers. Describe these layers and what is contained within them.

PCR Amplification

4. What is PCR?

5. What is a primer?

6. Describe what happens during the 3 cycles




7. After 30 cycles, how many copies of the initial DNA strand have been produced?


PCR Purification

8. To confirm that the PCR worked, three lanes are run that contain 3 materials. What materials are in the 3 lanes?

Lane 1
Lane 2
Lane 3

9. What is the overall purpose of the purification stage?

Sequencing Prep

10. Describe the “sequencing brew” that you added your purified PCR to.

11. The purpose of the second PCR is not to create identical copies like the first PCR you ran. What is the purpose of this PCR?

DNA Sequencing

12. What is the final PCR product, the stuff contained in your 12 tubes?

13. What is gel electrophoresis?

Sequence Analysis

14. What is BLAST?

15. What is the identity of the bacteria in your sample? Follow the steps listed on the page and be patient. BLAST data can take a while to search.

google doc

Other Resources on DNA

Coloring DNA - basic image of DNA and RNA for students to color following directions; includes questions and analysis

DNA Crossword - puzzle to practice basic terms related to DNA

Protein Synthesis Practice - use a codon chart to determine sequences of amino acids

Investigation: DNA Extraction for AP Biology - students extract DNA from different samples and write a lab report; with Claim, Evidence and Reasoning